Today, using an unlocked AT&T Huawei U2800A, when driving around, I received 3G with Tru using network name Tru[=T-Mobile]. The '3G' symbol was on my phone rather than the 'E' at my home. [See 'hole in the middle' below.] AT&T seems to only connect to Tru using Edge.
I do not do data so I really can't comment on performance, but I feel confident about 'connections'. T-Mobile is rapidly refarming 3G to 1900mHz band. So anyone with 1900 3G capibility should have confidence their phone can/will work 3G on Tru if you get to the USA. See map at below link.

Today, using an unlocked AT&T Huawei U2800A, when driving around, I received 3G with Tru using network name Tru[=T-Mobile]. The '3G' symbol was on my phone rather than the 'E' at my home. [See 'hole in the middle' below.] AT&T seems to only connect to Tru using Edge.

I took a recent ekit SIM on a similar trip and got the same results. 3G on T-Mobile, 2G[edge] on AT&T.

One thing about T-Mobile is that they have 3G (AWS) in places where they have no 2G service (e.g. Port St. Joe & Apalachicola, Fla.) They may have decided that allowing roamers on 3G (AWS or 1900) is good for business. OTOH, in many places ATT's 3G service has been saturated.

Frequently disappearance and reappearance of 3G coverage has been reported from many places where T-Mobile are refarming the PCS band. Either this is caused by the cells actually being switched on and off during the intial setup or the network is providing new cell reselection criteria to your phone which then switches back to 2G. You could switch your phone to 3G-only so you can rule out that your phone has been ordered by the network to use 2G instead of 3G.

Frequently disappearance and reappearance of 3G coverage has been reported from many places where T-Mobile are refarming the PCS band. Either this is caused by the cells actually being switched on and off during the intial setup or the network is providing new cell reselection criteria to your phone which then switches back to 2G. You could switch your phone to 3G-only so you can rule out that your phone has been ordered by the network to use 2G instead of 3G.

The phones I am using are unlocked AT&T Huawei U2800As.
I assume they are testing. Two days ago I had never seen 3G on T-Mobile here.
Phone is too simple to either have control of which network or 2G/3. And it goes back from 'E' to '3G' [2G/3G]. And back again. And back again. The airportal.de map for the first time today shows a 3G tower in the doughnut hole I talk about [zipcode=90240]. Not near me though. [Doughnut hole is bounded by following freeways: 60 to the North, 91 to the South, 710 to the West, 605 to the East {and out further East also}].

inquisitor, I always appreciate your knowledgable and wise insights.
thank you for responding.